If there's one thing I've learned in my time on OCC it's that you will get two very different opinions on this topic: the first will tout that only Hytran will do for our Cubs; it's what the manual recommends, it's what you should use. The second will say that the Cub transmission is nothing too special, just a basic hydraulic pump powering a set of gears so any hydraulic fluid will work. That being said, I (and many others) use "lesser" brands of hydraulic fluid and have for many many years with no issues. That being said, I look at it like I do engine oil: it's better to have fresh something than stale old goo. Change it/service it regularly and you'll be fine.
